New data presented from Cassini's Grand Finale

Spacecraft's final orbits shed light on inner workings and composition of of Saturn's rings and atmosphere.
By Laurel Kornfeld | Oct 18, 2017
Data collected by NASA's Cassini spacecraft during its Grand Finale and plunge into Saturn reveal new insights into Saturn's ring system and atmosphere.

The findings were presented at the American Astronomical Society's Division of Planetary Sciences meeting in Utah on October 16.

Among the data presented are two new mosaic images taken by the spacecraft from the unique position between the giant planet and the rings, including a panorama across the ringscape and a view of the rings emerging from behind the limb of the planet.

Cassini's imaging team described a phenomenon known as propellers, which are actually wakes produced by tiny moonlets. Six of these propellers were followed over the last several years, and the spacecraft managed to photograph all of them on the day before its fatal plunge into Saturn.

For four months, as Cassini carried out its Ring Grazing Orbits, its instruments captured various swarms of even smaller propellers.

Matt Tiscareno of the SETI Institute in Mountain View, California, who served as a member of the Cassini imaging team and as a project scientist, compared the physical processes carried out by the propellers to those of baby planets forming in the proto-planetary disks around new stars.

Images of Saturn's auroras captured in ultraviolet light by Cassini's Ultraviolet Imaging Spectrometer were assembled into a movie that was shown at the conference.

During its final days, Cassini served as an atmospheric probe, which was not part of original mission plans. The probe's Ion and Neutral Mass Spectrometer (INMS) observed molecules from Saturn's rings falling into its atmosphere, which extends almost back to the rings themselves.

Scientists expected water to be present in the ring materials, but INMS also revealed the presence of methane, which was surprising because such a volatile molecule was not believed to exist in Saturn's upper atmosphere or in its rings.

Lower altitudes in Saturn's atmosphere, imaged just before the spacecraft was destroyed, show even more complexity and are still being analyzed, noted INMS team associate Mark Perry of the Johns Hopkins University Applied Physics Laboratory (JHUAPL) in Maryland.

High-resolution photos of waves in Saturn's rings along with exact measurements of the masses of its moons indicate gravitational tugs of the various moons keep ring particles from dispersing outward.

Researchers hope the many measurements of Saturn's magnetic field conducted during the 22 Grand Finale orbits will finally help them determine the length of a Saturn day. This will require identifying the exact time length of Saturn's internal rotation, which in turn depends on determining whether the planet's magnetic field is tilted.

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